First high-resolution surface spectral clear-sky ultraviolet radiation dataset across China (1981–2023): development, validation, and variability

Cloud's and the Earth's Radiant Energy System (CERES) is an investigation into the role of clouds and radiation in the Earth's climate system. Four CERES scanning thermistor bolometer instruments are currently in orbit. Flight model 1 (FM1) and 2 (FM2) are aboard the Earth Observing System (EOS) Terra satellite and FM3 and FM4 are aboard the EOS Aqua satellite. Each CERES instrument measures in three broadband radiometric regions: the shortwave (SW 0.3-5μm), total (0.3- > 100μm), and window (8-12μm). It has been found that both CERES instruments on the Terra platform imply that the SW flux scattered from the Earth had dropped by up to 2% from 2000 to 2004. No climatological explanation for this drop could be found, suggesting the cause was a drift in both the Terra instruments. However, the onboard calibration lamps for the SW channels do not show a change in gain of this magnitude. Experience from other satellite missions has shown that optics in the orbital environment can become contaminated, severely reducing their transmission of ultra-violet (UV) radiation. Since the calibration lamps emit little radiance in the UV spectral region it was suggested that contaminates could be responsible for an undetectable 'spectral darkening' of the CERES SW channel optics and hence the apparent drop in SW flux. Further evidence for this was found by looking at the comparison between simultaneous measurements made by FM1 and FM2. The proposed mechanisms for contaminant build up would not apply to a CERES instrument operating in the normal cross track scan mode. Indeed it was found from the comparison between CERES instruments on Terra that the response of the instrument operating in rotating azimuth plane (RAPS) mode consistently dropped relative to the other cross track instrument. Since at all times one of the instruments operates in cross track mode, where it is not subject to spectral darkening, it allowed that unit to be used as a calibration standard from which the darkening of the other RAPS instrument can be measured. A table of adjustment coefficients to compensate for this spectral darkening are therefore derived in this paper. These figures are designed to be multiplied by SW fluxes or radiances produced in the climate community using Edition 2 CERES data. SW CERES measurements that have been revised using these coeffcients are therefore to be referred to as ERBE-like Edition2_Rev1 or SSF Edition2B_Rev1 data in future literature. Current work to fully characterize the effect of spectral darkening on the instrument spectral response before the release of Edition 3 data is also described.

Abstract. Radiative fluxes at the top of the atmosphere (TOA) from the Clouds and the Earth's Radiant Energy System (CERES) instrument are fundamental variables for understanding the Earth's energy balance and how it changes with time. TOA radiative fluxes are derived from the CERES radiance measurements using empirical angular distribution models (ADMs). This paper evaluates the accuracy of CERES TOA fluxes using direct integration and flux consistency tests. Direct integration tests show that the overall bias in regional monthly mean TOA shortwave (SW) flux is less than 0.2 Wm−2 and the RMSE is less than 1.1 Wm−2. The bias and RMSE are very similar between Terra and Aqua. The bias in regional monthly mean TOA LW fluxes is less than 0.5 Wm−2 and the RMSE is less than 0.8 Wm−2 for both Terra and Aqua. The accuracy of the TOA instantaneous flux is assessed by performing tests using fluxes inverted from nadir- and oblique-viewing angles using CERES along-track observations and temporally and spatially matched MODIS observations, and using fluxes inverted from multi-angle MISR observations. The averaged TOA instantaneous SW flux uncertainties from these two tests are about 2.3 % (1.9 Wm−2) over clear ocean, 1.6 % (4.5 Wm−2) over clear land, and 2.0 % (6.0 Wm−2) over clear snow/ice; and are about 3.3 % (9.0 Wm−2), 2.7 % (8.4 Wm−2), and 3.7 % (9.9 Wm−2) over ocean, land, and snow/ice under all-sky conditions. The TOA SW flux uncertainties are generally larger for thin broken clouds than for moderate and thick overcast clouds. The TOA instantaneous daytime LW flux uncertainties derived from the CERES-MODIS test are 0.5 % (1.5 Wm−2), 0.8 % (2.4 Wm−2), and 0.7 % (1.3 Wm−2) over clear ocean, land, and snow/ice; and are about 1.5 % (3.5 Wm−2), 1.0 % (2.9 Wm−2), and 1.1 % (2.1 Wm−2) over ocean, land, and snow/ice under all-sky conditions. The TOA instantaneous nighttime LW flux uncertainties are about 0.5–1 % (< 2.0 Wm−2) for all surface types. Flux uncertainties caused by errors in scene identification are also assessed by using the collocated CALIPSO, CloudSat, CERES and MODIS data product. Errors in scene identification tend to underestimate TOA SW flux by about 0.6 Wm−2 and overestimate TOA daytime (nighttime) LW flux by 0.4 (0.2) Wm−2 when all CERES viewing angles are considered.

Clouds and the Earth's Radiant Energy System (CERES) instruments were designed to measure the reflected shortwave and emitted longwave radiances of the Earth's radiation budget and to investigate the cloud interactions with global radiances for the long-term monitoring of Earth's climate. CERES instrument has three scanning thermistor bolometers that measure broadband radiances in the shortwave (0.3 to 5.0 micrometer), total (0.3 to >100 micrometer) and 8 - 12 micrometer water vapor window regions. Four CERES instruments (Flight Models1 through 4) are flying aboard EOS Terra and Aqua platforms with two instruments aboard each spacecraft. The pre-launch accuracy requirements for CERES were 1.0% in the shortwave and 0.5% in longwave regions. The in-flight calibration of CERES sensors are carried out using the internal calibration module (ICM) comprising of blackbody sources and tungsten lamp, and a solar diffuser plate known as the Mirror Attenuator Mosaic (MAM). The ICM and MAM calibration results are instrumental in understanding the ground to flight shift and in-flight drifts in CERES sensors' gains. Inter and intra instrument validation studies are conducted on the CERES measurements to monitor the behavior of the sensors in various spectral regions. Targets such as deep convective clouds and tropical ocean are used to evaluate the sensors' stability within an instrument. With two CERES instruments on same platform, inter comparison of similar sensor measurements viewing the same geolocation are also conducted. The results from these individual studies have collectively given an understanding of each CERES sensor's behavior in different spectral regions. This paper discusses the results from each of these studies which facilitated the correction of CERES data products with a calibration stability better than 0.2%. Keywords: CERES, EOS Instrument, Radiometry, Calibration, Validationt

Clouds and the Earth's Radiant Energy System (CERES) instruments were designed to provide accurate measurements for the long-term monitoring of Earth's radiation energy budget. The CERES instrument consists of three scanning thermistor bolometer sensors with built-in flight calibration systems. The three sensors measure the broadband radiances in the shortwave (0.3-5.0 /spl mu/m), total (0.3->100 /spl mu/m) and 8-12 /spl mu/m water vapor window regions. The CERES sensors were calibrated using the internal calibration module sources within the Radiometric Calibration Facility at TRW, Redondo Beach, California, and in-flight on a biweekly basis. This paper discusses the in-flight calibration procedures for the CERES sensors. The radiometric performance results of the Proto-Flight Model CERES instrument on the ground and aboard the TRMM spacecraft during the first year of its mission life are also presented.

The ultimate goal of NASA's Terra mission is to unravel the mysteries of climate and environmental change. The instruments on board the Terra spacecraft are collecting global data sets needed to study the interrelationships inherent in the Earth's coupled atmosphere-land-ocean-biosphere system. Issues such as the Earth's energy balance, global cloudiness, the effects of atmospheric aerosols, and the impact of trace gases on climate can be addressed with simultaneous data from instruments such as the Clouds and the Earth's Radiant Energy System (CERES), the Multi-angle Imaging SpectroRadiometer (MISR) and the Measurements Of Pollution In The Troposphere (MOPITT). An important feature of the experiments onboard Terra is the ability to obtain data from multiple instruments viewing the same phenomena. CERES, MISR and MOPITT data available from the Atmospheric Sciences Data Center (ASDC) at NASA's Langley Research Center are used to demonstrate various complementary views of the Earth system. Examples are given of spatially and temporally coincident data covering phenomena such as aerosol concentrations from dust storms, and carbon monoxide and smoke associated with fires. CERES uses broadband radiometric measurements in three channels to provide both solar-reflected and Earth-emitted radiation throughout the atmosphere and, in combination with simultaneous measurements from instruments such as the Moderate Resolution Imaging Spectrometer (MODIS), provides new information on cloud properties. MISR obtains precisely calibrated images taken simultaneously at nine different angles and four wavelengths (blue, green, red and near-infrared) to provide data related to aerosols, clouds, and the Earth's surface. MOPITT is a scanning radiometer designed to measure tropospheric profiles and total column amount of carbon monoxide on both the day and night portions of an orbit. Information about the available CERES, MISR and MOPITT data products, and how to obtain them can be found at the ASDC web site: http://eosweb.larc.nasa.gov

The Clouds and the Earth's Radiant Energy System (CERES) instruments measure the two key components of the Earth's Radiation Budget, the reflected shortwave and the emitted longwave energy. The CERES instrument consists of three scanning thermistor bolometers that measure the broadband radiances in the shortwave (0.3 to 5.0 micrometer), total (0.3 to >100 micrometer) and 8-12 micrometer water vapor window regions. Four CERES instruments (Flight Models 1 through 4) are flying aboard EOS Terra and Aqua platforms with two instruments aboard each spacecraft. The accuracy requirements of the CERES sensors are achieved through the prelaunch calibrations and on-orbit calibration activities. The CERES detector gain and the response function are determined by the prelaunch ground calibrations. The post launch calibration of CERES sensors are carried out using the internal calibration module (ICM) comprising of blackbody sources and quartz-halogen tungsten lamp, and a solar diffuser plate known as the Mirror Attenuator Mosaic (MAM). The ICM calibration results are instrumental in determining the changes in CERES sensors' gains after launch from the pre-launch determined values and the on-orbit gain variations. In addition to the broadband response changes derived from the on-board blackbody and the tungsten lamp, the shortwave and the total sensors show a spectral change in responsivity in the shorter wavelength region below one micron that were brought to light through vicarious studies. The spectral change was attributed to the instrument operational modes and the corrections were derived using the sensor radiance comparisons. This paper covers the on-orbit behavior of CERES sensors and the determination of the sensor response changes utilizing the in-flight calibration and the radiance comparisons. The corrections for the sensor responses were incorporated in the radiance calculations of CERES Edition3 data products.

Improved estimation of the global top-of-atmosphere albedo from AVHRR data

Clouds and the Earth's Radiant Energy system (CERES) sensors provide accurate measurements for the long-term monitoring of the Earth's radiation budget components. The three scanning thermistor bolometer sensors on CERES measure broadband radiances in the shortwave (0.3 to 5.0 micrometer), total (0.3 to >100 micrometer) and in 8 - 12 micrometer water vapor window regions. Currently four of the CERES instruments (Flight Models 1 through 4 [FM1 - FM4]) are flying aboard EOS Terra and Aqua platforms with two instruments aboard each spacecraft. The sensor calibrations are performed with onboard blackbody sources and a tungsten lamp as well as a solar diffuser plate known as the Mirror Attenuator Mosaic (MAM). The calibration results collectively depict the ground to orbit shifts and the on-orbit drifts in the sensor reponses. Deep convective clouds and tropical ocean are used as validation targets to understand the sensors' stability on-orbit. With two CERES instruments on the same platform, comparison of measurements from similar sensors viewing the same geolocation are performed. The different calibration and validation studies performed on CERES bring to light the radiometric gain and spectral variation of the sensors from pre and post launch. This paper discusses briefly the contribution of each calibration and validation study in understanding CERES sensors' behavior. It also shows the results from these studies which enabled to correct the data products with a calibration stability of better than 0.2%.

Clouds and the Earth's Radiant Energy System (CERES) is a National Aeronautics and Space Administration (NASA) investigation to examine the role of clouds in the radiative energy flow through the Earth-atmosphere system. The first CERES scanning radiometer was launched on November 27, 1997 into a 35 inclination, 350 km altitude orbit, on the Tropical Rainfall Measuring Mission (TRMM) spacecraft. The CERES instrument consists of a three channel scanning broadband radiometer. The spectral bands measure shortwave (0.3 - 5 microns), window (8 - 12 microns), and total (0.3 - 100 microns) radiation reflected or emitted from the Earth-atmosphere system. Each Earth viewing measurement is geolocated to the Earth fixed coordinate system using satellite ephemeris, Earth rotation and geoid, and instrument pointing data. The interactive CERES coastline detection system is used to assess the accuracy of the CERES geolocation process. By analyzing radiative flux gradients at the boundaries of ocean and land masses, the accuracy of the scanner measurement locations may be derived for the CERES/TRMM instrument/satellite system. The resulting CERES measurement location errors are within 10% of the nadir footprint size. Precise pointing knowledge of the Visible and Infrared Scanner (VIRS) is required for convolution of cloud properties onto the CERES footprint; initial VIRS coastline results are included.

본 연구에서는 대기 상단에서 반사된 복사와 지표면에서 흡수된 복사에너지가 서로 선형 관계임을 보인 기존의 알고리즘을 MODerate resolution Imaging Spectroradiometer (MODIS) 관측 자료에 적용시킬 수 있도록 개선하여 하향 및 순 태양 복사에너지를 산출하였다. 비교 검증을 수행하기 위해 Clouds and the Earth's Radiant Energy System (CERES) 센서와 강릉원주대학교(GWNU), 미국의 Atmospheric Radiation Measurement (ARM) 관측소의 지상 일사계 자료를 사용하였다. 지구 에너지 수지와 관련하여 지표면에서의 복사에너지를 비교하기에 앞서 알고리즘을 통한 산출 결과와 CERES 자료의 대기 상단 복사에너지를 비교한 결과, 결정계수가 0.9이상을 보여 상당히 유사함을 보였지만 Root-Mean-Square-Deviation (RMSD) 값이 다소 차이가 있는 것으로 나타났고 하향과 순 태양 복사에너지도 비슷한 결과를 얻었다. 강릉원주대학교 자료와 비교한 결과, 본 연구의 알고리즘을 통해 산출된 결과가 CERES 자료보다 작은 RMSD를 보임으로서 더 높은 정확도를 보였다. 한편, ARM 관측소의 경우 하향 태양 복사에너지의 평균적인 RMSD가 CERES 자료에 비해 다소 크게 산출되었지만 순 태양 복사에너지의 경우 비슷한 결과가 나타났으며 시 공간 해상도를 고려하였을 때 상당히 유사한 경향을 보이고 있음을 확인하였다. 본 연구에서 파악된 문제점에 대한 개선을 통해 향후 지상 관측을 대신하여 위성 관측으로부터 지표면에서의 하향 및 순 태양 복사에너지 자료를 고해상도로 제공하는데 유용하게 활용될 수 있을 것으로 기대된다. In this study, the net solar radiation fluxes at the surface are retrieved by updating an existing algorithm to be applicable for MODerate resolution Imaging Spectroradiometer (MODIS) observations, in which linear relationships between the solar radiation reflected from the top of atmosphere and the net surface solar radiation are employed. The results of this study have been evaluated through intercomparison with existing Clouds and the Earth's Radiant Energy System (CERES) data products and ground-based data from pyranometers at Gangneung-Wonju National University (GWNU) and the Southern Great Plains (SGP) of observatory of Atmospheric Radiation Measurement (ARM) site. Prior to the comparison of the surface radiation energy in relation to the energy balance of the earth, the radiation energy of the upper part of the atmosphere was compared. As a result, the coefficient of determination was over 0.9, showing considerable similarity, but the Root-Mean-Square-Deviation (RMSD) value was somewhat different, and the downward and net solar-radiation energy also showed similar results. The surface solar radiation data measured from pyranometers at Gangneung-Wonju National University (GWNU) and Atmospheric Radiation Measurement (ARM) observatory are used to validate the solar radiation data produced in this study. When compared to the GWNU, The results of this study show smaller RMSD values than CERES data, showing slightly better agreements with the surface data. On the other hand, when compared with the data from ARM SGP observatory, the results of this study bear slightly larger RMSD values than those for CERES. The downward and net solar radiation estimated by the algorithm of this study at a high spatial resolution are expected to be very useful in the near future after refinements on the identified problems, especially for those area without ground measurements of solar radiation.

Nine months of the Clouds and the Earth's Radiant Energy System (CERES)/Tropical Rainfall Measuring Mission (TRMM) broadband fluxes combined with the TRMM visible infrared scanner (VIRS) high-resolution imager measurements are used to estimate the daily average direct radiative effect of aerosols for clear-sky conditions over the tropical oceans. On average, aerosols have a cooling effect over the Tropics of 4.6 ± 1 W m–2. The magnitude is ≈2 W m–2 smaller over the southern tropical oceans than it is over northern tropical oceans. The direct effect derived from CERES is highly correlated with coincident aerosol optical depth (τ) retrievals inferred from 0.63-μm VIRS radiances (correlation coefficient of 0.96). The slope of the regression line is ≈−32 W m–2 τ–1 over the equatorial Pacific Ocean, but changes both regionally and seasonally, depending on the aerosol characteristics. Near sources of biomass burning and desert dust, the aerosol direct effect reaches −25 to −30 W m–2. The direct effect from CERES also shows a dependence on wind speed. The reason for this dependence is unclear—it may be due to increased aerosol (e.g., sea-salt or aerosol transport) or increased surface reflection (e.g., due to whitecaps). The uncertainty in the tropical average direct effect from CERES is ≈1 W m–2 (≈20%) due mainly to cloud contamination, the radiance-to-flux conversion, and instrument calibration. By comparison, uncertainties in the direct effect from the Earth Radiation Budget Experiment (ERBE) and CERES “ERBE-like” products are a factor of 3–5 times larger.

Clouds and the Earth's Radiant Energy System (CERES) instruments were designed to measure the reflected shortwave and emitted longwave radiances of the Earth's radiation budget and to investigate the cloud interactions with global radiances for the long-term monitoring of Earth's climate. The three scanning thermistor bolometer sensors on CERES measure broadband radiances in the shortwave (0.3 to 5.0 micrometer), total (0.3 to ≫100 micrometer) and in 8 - 12 micrometer water vapor window regions. Four of the CERES instruments (Flight Models1 through 4) fly aboard Earth Observing System (EOS) Terra and Aqua platforms with two instruments aboard each spacecraft, in 705 KM sun-synchronous orbits of 10:30 AM and 1:30 PM equatorial crossing time. The CERES data products consist of geolocated instantaneous unfiltered radiances through temporally and spatially averaged Top of the Atmosphere (TOA) and Surface fluxes. These CERES data products have achieved a higher level of calibration accuracy and stability than the previous ERBE products. This improvement was attained through the development of a rigorous and comprehensive radiometric validation protocol comprising of studies covering different spatial, spectral and temporal time scales. The in-flight calibration of CERES sensors are carried out using the internal calibration module (ICM) comprising of blackbody sources and tungsten lamp, and a solar diffuser plate known as the Mirror Attenuator Mosaic (MAM). The ICM and MAM calibration results are instrumental in understanding the ground to flight shift and in-flight drifts in CERES sensors' gains.

Clouds and the Earth's Radiant Energy System (CERES) Flight Model 5 (FM5) instrument is designed to continue the long-term monitoring of the Earth's radiation budget. CERES has three sensor units that measure radiation in the 0.3 - 5.0 μm, 0.3 - >;100 μm and 8 - 12 μm wavelength regions. Prelaunch characterization of the sensors to determine their radiometric gain and spectral response function was performed in September 2008. The longwave calibrations was achieved using a Narrow Field of view Blackbody (NFBB) that is tied to the International Scale of 1990 (ITS '90). The calibration in the shortwave region is performed using the Shortwave Reference Source (SWRS) along with the Transfer Active Cavity radiometer (TACR). The spectral responsivity of the sensors is measured with narrow band filters for region below 2.5 microns and with a Fourier Transform Spectrometer (FTS) system above the 2.5 micron region. The calibration with CERES on-board sources were also performed during pre-launch testing which will serve as a traceability standard to carry the ground determined radiometric gains to orbit. This paper covers the CERES calibration methodology used in the ground calibration testing of FM5 sensors performed in 2008.

NASA's Earth Observing System (EOS) is part of an international program for studying the Earth from space using a multiple-instrument, multiple-satellite approach. The Clouds and the Earth's Radiant Energy System (CERES) experiment is designed to monitor changes in the Earth s radiant energy system and cloud systems and to provide these data with sufficient simultaneity and accuracy to examine critical cloud/climate feedback mechanisms which may play a major role in determining future changes in the climate system. The first EOS satellite (Terra), scheduled for launch this year, and the EOS-PM satellite, to be launched in late 2000, will each carry two CERES instruments. The first CERES instrument was launched in 1997 on the Tropical Rainfall Measuring Mission (TRMM) satellite. The CERES TRMM data show excellent instrument stability and a factor of 2 to 3 less error than previous Earth radiation budget missions. The first CERES data products have been validated and archived. The data consist of instantaneous longwave and shortwave broadband radiances, top-of-atmosphere fluxes, scene types, and time and space averaged fluxes and albedo. A later data product will combine CERES radiances and high- resolution imager data to produce cloud properties and fluxes throughout the atmosphere and at the surface.

Clouds and the Earth's Radiant Energy System (CERES) instruments were designed to measure the reflected shortwave and emitted longwave radiances of the Earth’s radiation budget and to investigate the cloud interactions with global radiances for the long-term monitoring of Earth's climate. The three scanning thermistor bolometer sensors on CERES measure broadband radiances in the shortwave (0.3 to 5.0 micrometer), total (0.3 to <100 micrometer) and in 8 - 12 micrometer water vapor window regions. Of the five CERES instruments that are currently in operation, four of the CERES instruments (Flight Models1 through 4) fly aboard Earth Observing System (EOS) Terra and Aqua platforms with two instruments aboard each spacecraft, in 705 KM sun-synchronous orbits of 10:30 AM and 1:30 PM equatorial crossing time. A rigorous and comprehensive radiometric calibration and validation protocol comprising of various studies was developed to evaluate the calibration accuracy of the CERES instruments. The in-flight calibration of CERES sensors are carried out using the internal calibration module (ICM) comprising of blackbody sources and quartzhalogen tungsten lamp, and a solar diffuser plate known as the Mirror Attenuator Mosaic (MAM). The ICM calibration results are instrumental in determining the changes in CERES sensors’ gains after launch from the prelaunch determined values and the on-orbit gain variations. In addition to the broadband response changes derived from the on-board blackbody and the tungsten lamp, the shortwave and the total sensors show a spectrally dependent drop in responsivity in the shorter wavelegth region below one micron that were brought to light through validation studies. The spectrally dependent changes were attributed to the instrument operational modes and the corrections were derived using the sensor radiance comparisons. This paper covers the on-orbit behavior of CERES sensors aboard the Terra and Aqua spacecraft and the determination of the sensor response changes utilising the in-flight calibration and the radiance measurement comparisons viewing various targets. The corrections for the sensor response changes were incorporated in the radiance calculations of CERES Edition3 data products.